Okay, I loved Banana Fish so much when I watched it, but it does have its flaws, and I'm not going to shy away from talking about them just because I like it.
If we're going to be honest, the characters could've been written a whole lot better. I found myself completely disconnected from anyone who wasn't Ash, because he's the only character that recieved enough attention to be called a well-written and fully developed character. Shorter, Skip(er)?, Max, etc, were all one-note, and seemingly had little to nothing to do with the story (more on that later). I did like all of the characters, though. I'm not saying that I hated any of them, but it's pretty obvious that the writers didn't spend enough time developing them. And I'm sorry to say this, but Eiji had absolutely no real personality. I still love him, though.
Moving on to the plot. The plot also could've used a bit of work, in my opinion. In the beginning of the story, the plot was more at the forefront and towards the end it took a very big backseat to the Ash and Eiji show. Now, I'm not sure if this was intentional or not, and let me explain why. This is a very common thing in action movies/t.v. shows/games, even (mainly zombie related), where the plot, (also known as the immediate threat/danger to the characters' lives) will become "white noise" to the characters' development. If you're confused, let me give you an example. In the Telltale game, The Walking Dead, it's about the zombie apocalypse. THAT'S the plot of the game. But the zombies aren't really the focus. It's more so about the interactions with the characters and how they grow and regress as people due to all of the messed up things that they have to do to survive. The apocalypse itself is the "white noise" I was talking about earlier. So in Banana Fish, "the white noise" would be everyone trying to kill them and capture them, and how Ash and Eiji (and the other characters, of course, but...it's really not about the other characters, let's be real) connect and develop through all of that would be the main focus of the story. BUT there is a problem that arises with this "theory". In order to pull off what the Telltale game did successfully, you would have to have well-written characters, which isn't what Banana Fish has.
Or maybe the story's just poorly written and I'm looking too deep into it, but I'm desperately trying to give it the benefit of the doubt.
Now, because I've said that the plot wasn't handled the right way, let's talk about the characters again. A lot of these characters that are a part of Ash's "main crew" and the ones that help Ash throughout the story are kind of useless, and the story probably would be able to move forward without them. Ibe, Shorter, Skip, Cain, etc.
Anyway, I still love this show with all my heart, but it's not the best. I can't wait to read the manga, though, because I heard it's a lot different.